An electronic paper display may be formed by connecting a thin layer of transparent plastic small beads, which are randomly dispersed, to a surface of a sheet. The beads have two hemispheres that have two contrasting colors, such as black and white, red and white or the like. The hemispheres are electrically charged to exhibit an electrical dipole. For example, the color red on a first hemisphere may be associated with a negative charge and the color white on a second hemisphere may be associated with a positive charge. The hemispheres of the beads are contained within an oil-filled cavity, and rotate within the oil-filled cavities based on electrical charges that attract or repel the electrically charged hemispheres. Thus, the sheet receiving the beads and/or the oil-filled cavities may be required to be stiff and rigid to prevent puncturing of the cavities or damaging of the cavities or the hemispheres of the beads by, for example crushing, flattening or the like.
A voltage is applied to the surface of the sheet via one or more electrode plates associated with the sheet. The voltage applied by the electrode plates provides an electric field which may attract one of the hemispheres of one or more of the beads based on the charge associated with that hemisphere. As a result, one or more of the beads are rotated by the attractive forces between one of the hemispheres of the beads, the charge associated with the hemispheres of the beads, and the electric field created by the electrode plates. As a result, the hemispheres of the beads may rotate to present one of the hemispheres in a viewing direction on the electronic paper. By rotating one or more beads to present one of the hemispheres for each bead, the hemispheres may form or may display an image on the electronic paper. As a result, the electric field applied to the surface of the sheet by the electrode plates creates the image that is viewable from a viewing direction of the electronic paper.
However, connecting a thin layer of the beads having the oil-filled cavities to the surface of the sheet to form the electronic paper is often time consuming and costly. Additionally, a resolution of the images formed on the surface of the electronic paper by the one or more beads tends to be lower because a pixel count per square inch for the thin layer of beads formed on the surface of the sheet is often minimal as compared to a resolution of a conventional display, such as an LCD. Further, increasing the pixels per square inch by increasing a number of beads per square inch on the surface of the sheet is burdensome because difficulties exist for positioning the oil-filled cavities at specific locations corresponding to specific pixels or subpixels. Moreover, sealing an increased number of oil-filled cavities to the surface of the sheet to increase the pixels per square inch is inconvenient for forming electronic paper via the beads. The rotation of the beads to display different hemispheres often tends to be too slow for some display purposes, such as screens and the like. As a result, forming electronic paper with the beads having oil-filled cavity has an increased probability for manufacturing problems and often elevates production costs for the electronic paper.
Furthermore, dyes or colored pigments that are traditionally used to provide color in electrophoretic inks scatter or absorb a portion of ambient light. As a result, a lower percentage of light reflects back towards or comes back towards a viewer because of the portion of ambient light scattered or absorbed by the dyes or colored pigments. A color intensity is thus low in the color contrast display. More specifically, the color contrast between white areas, such as background areas, and color areas, such as image areas, is poor compared to the same color contrast in other backlit displays or light emitting displays. Further, the dyes or colored pigments may absorb ultraviolet (UV) light that results in degraded appearance over time.
A need, therefore, exists for a system and a method for forming better color contrast electrophoretic displays with enhanced color intensity. Further, a need exists for a system and a method for forming electrophoretic ink that reduces scattering or absorption of ambient light. Still further, a need exists for a system and a method for a forming electrophoretic ink that reflects a high percentage of light back towards a viewer of a display device having the electrophoretic ink. Furthermore, a need exists for a system and a method for forming electrophoretic ink that may prevent UV light absorption by colored pigments to reduce degradation of appearance over time.